Carburetor tuning device

ABSTRACT

A DEVICE FOR USE IN THE ADJUSTMENT OF THE CARBURETTORS OF INTERNAL COMBUSTION ENGINES BY PRODUCING A WHISTLE SOUND SIGNAL. A CYLINDRICAL CHAMBER COVERED AT EACH END BY A FLAT END WALL. A FIRST INLET IN OTHER END WALL, AND A SECOND INLET THROUGH A SIDE WALL OF THE CHAMBER. AN AXIAL WHISTLE WALL IN THE CHAMBER FROM END TO END HAVING A WHISTLE OPENING NEAR THE FIRST INLET. A MASK ON THE SIDE WALL OF THE CHAMBER ADUSTABLE OVER THE SECOND INLET TO VARY ITS OPENING, THEREBY TO VARY THE VELOCITY OF AIR FLOW FROM THE FIRST INTAKE TO THE OUTLET UNTIL THE WHISTLE SOUND SIGNAL IS PRODUCED. THEN THE AIR INTAKES OF THE CARBURETTORS ARE ADJUSTED TO PRODUCE THE SAME WHISTLE SOUND.

March 16, 1971 B BOWLES CARBURE'FI'OR- TUNING DEVICE Filed March 24, 1969 United States Patent O 3,570,306 CARBURETOR TUNING DEVICE Breck Bowles, Hampton Wick, England, assignor to Les Leston Limited Filed Mar. 24, 1969, Ser. No. 809,667 Claims priority, application Great Britain, May 13, 1968, 22,688/68 Int. Cl. G01m /00 U.S. Cl. 73-119 3 Claims ABSTRACT OF THE DISCLOSURE A device for use in the adjustment of the carburettors of internal combustion engines by producing a whistle sound signal. A cylindrical chamber covered at each end by a flat end wall. A first inlet in other end wall, and a second inlet through a side wall of the chamber. An axial whistle wall in the chamber from end to end having a whistle opening near the first inlet. A mask on the side wall of the chamber adjustable over the second inlet to vary its opening, thereby to vary the velocity of air fiow from the first intake to the outlet until the whistle sound signal is produced. Then the air intakes of the carburettors are adjusted to produce the same whistle sound.

BACKGROUND OF THE INVENTION This invention is concerned with the adjustment of the carburettors of internal combustion engines of the kind that have two or more carburettors. The balancing of the two or more carburettors of a car or other vehicle engine is a quite skilled job which must be performed correctly if the engine is to function efficiently and economically. Basically, two matching operations are required, one in respect of the fuel/ air mixture screws and the other in respect of the air intakes of the two or more carburettors. The first of the two operations that have just been mentioned is relatively simple requiring only the turning of two screws by equal amounts from similar starting positions. The second operation, however, is much more difiicult and it is an object of the present invention to provide a simple device which will greatly reduce the difficulty without it being necessary to use an expensive flow-meter or the like.

According to the invention, there is provided a device for use in the adjustment of the carburettors of internal combustion engines, the device comprising a chamber formed with an air outlet and with first and second air inlets, means to vary the open area of the second air inlet between maximum and minimum values and a whistle mmeber located within the chamber and arranged to be fed with air from the first inlet during use of the device. i

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. '1 is an elevation of a device in accordance with the invention,

FIG. 2 is a plan view of the device, and

FIG. 3 is a section of the device taken along the line IIIIII of FIG. 1.

DETAILED DESCRIPTION Referring to the drawings, the device which is illustrated has a height of about 2 inches and an over all diameter of approximately 2 /3 inches. It is preferred, but is not absolutely essential, that the device should be formed substantially wholly from synthetic plastics materials and, although the drawings show certain parts 3,570,306 Patented Mar. 16, 1971 formed from transparent materials, it is preferred that opaque materials should be employed for the whole of the device. The device comprises a circular cylindrical chamber 1 having upper and lower end plates 2 and 3 respectively. It is emphasized that the terms upper and lower that have just been used are employed only for convenience in describing the device as disposed in the way which it appears in the accompanying drawings. As can be seen best in FIG. 3 of the drawings, the lower end plate 3 has a diameter such that a rim 4 is formed which projects beyond the convex curved surface of the chamber 1 by a distance of about A of an inch.

The lower end plate 3 of the chamber 1 has an air outlet in the form of a circular hole 5 having a diameter of a little less than 1 inch. The upper end plate 2 is formed with a first air inlet in the form of a rectilinear slot 6 having a length of about of an inch and a width of about of an inch. The chamber 1 is provided with a second air inlet in the form of a slot 7 in the curved wall of the chamber. The slot 7 subtends an angle of slightly more than at the longitudinal axis of the chamber -1 and has a width (in a direction parallel to the axis which has just been mentioned) of slightly in excess of /2 an inch. The slot 7 has a curved length around the wall of the chamber 1 of a little less than 2 inches. Means is provided to vary the open area of the slot 7 between a maximum value equivalent to interrupted opening of said slot and a minimum value of nothing in which the slot 7 is completely closed. Said means takes the form of a C-shaped mask 8 the centre of curvature of which is coincident with the longitudinal axis of the chamber 1 and the width of which (in a direction parallel to the last-mentioned axis) is a little in excess of one inch.

A whistle member 9 of tubular configuration is disposed internally of the chamber 1 with one end of the tube fastened to the inner surface of the end plate 3 alongside the hole 5 in sealing relationship with said end plate. The internal diameter of the tube is about of an inch. The end of the tubular whistle member 9 remote from the plate 3 has a portion which is fixed to the upper end plate 2 but the remainder thereof is bevelled away from the plate 2, the plane of the bevel being inclined to that of the plate 2 at an angle of approximately 40. Part of the open bevelled end of the tubular whistle member 9 is closed by a plate which has an edge 10 that is in approximate alignment with one of the edges of the slot 6, it being noted that air entering the chamber 1 through the slot 6 will tend to take an inclined path therethrough towards the hole 5, or the hole 5 and the slot 7, and will thus impinge upon the edge 10 to produce a whistling sound.

When the device which has been described is to be employed in matching the air intakes of two or more carburettors, the operator proceeds by adjusting the common idling control of said carburettors until a setting is found in which the vehicle engine or other internal combustion engine runs evenly. This can be judged quite easily by anyone having only a rudimentary knowledge of the maintenance of internal combustion engines and it will almost always be found that a convenient setting is readily attainable unless at least one carburettor is incomplete or is seriously worn or damaged in some way. As soon as an appropriate setting has been attained, the operator places the device over the air intake of a first one of the carburetors in such a way that the lower end plate 3 bears against said air intake with the latter surrounding the hole 5. If desired, the exposed surface of the end plate 3 may be provided with a layer of felt, synthetic plastic foam, rubber or the like to ensure a good seal between the plate 3 and the air intake under these conditions, but it has been found that this is a refinement which is not absolutely necessary. The mask 8 will have been moved around the chamber 1, before the adjustment is commenced, to a position in which the slot 7 is fully open so that air can pass from that slot, and from the slot 6, direct to the air outlet afiorded by the hole 5. The operator holds the chamber 1 against the air intake of the first carburettor with one hand and uses his other hand to turn the mask 8 slowly around the chamber 1 with a consequent progressive reduction in the open cross-sectional area of the slot 7. A point will be reached at which the progressively increasing rate of air fiow through the slot 6 that is of fixed open cross-sectional area will cause the whistle member 9 to emit a very loud whistling note.

As soon as the whistle member 9 of the device gives a signal in the manner described above, the operator removes the device from the air intake of the first carburettor being careful not to disturb the angular setting of the mask 8 about the chamber 1 and places the lower end plate 3 against the air intake of the other, or a second, carburettor in such a way that the hole 5 is in open communication with said air intake. The operator now holds the chamber 1 with one hand and uses his other hand to make an adjustment (usually with the aid of a small screwdriver) of the so-called butterfly valve of said other or second carburettor. When the butterfly valve has been adjusted to a setting in which the whistle member 9 once again produces a signal, the rate of flow of air per unit time through the other or second carburettor will be substantially identical to that in the case of the first carburettor. It will be self-evident that, if there are more than two carburettors, the remaining one(s) is/are dealt with in the same way as the second carburettor.

The device which has been described enables both pro fessional and amateur motor mechanics to perform a somewhat difficult operation which normally needs considerable skill and experience with great ease, the device being of very simple and robust construction that is very much lower in cost than flow-meters or the like that are conventionally used in performing this operation. Moreover, it has been found that a device in accordance with the invention is extremely sensitive being able to detect very minor variations in the rate of air flow that do not register at all on a conventional flow-meter.

The described device has been stated to be formed substantially wholly form synthetic plastics materials but it will be understood that the invention is not limited 4 to this aspect and that other materials may be employed if preferred. The projecting rim 4 of the lower end plate 3 prevents the mask 8 from being withdrawn downwardly (in the drawing) from the chamber 1 and, if preferred, some form of ring, flange or other projection may be fastened to the external surface of the chamber 1 after the mounting of the mask thereon to ensure that the mask 8 cannot be removed upwardly (in the drawing) from said chamber. However, once again, this is a refinement which is not absolutely necessary.

What is claimed is: l].- A device for use in the adjustment of the carburettors of internal combustion engines, comprising a cylindrical chamber, end walls covering the ends of said chamber, one of said end walls having an air outlet, the other end wall having a first air inlet, the cylindrical portion of said chamber having a second air inlet. an axial whistle wall within said chamber opposite said second air inlet and having a whistle opening in operative relation to said first air inlet, and means to vary the opening of said second air inlet thereby to vary the velocity of the air flowing from said first inlet to said air outlet to an adjustment for producing a sound signal. 2. The device according to claim 1, and a portion of said whistle wall adjacent to said first inlet having an edge at said whistle opening and being inclined away from said first air inlet and toward said second air inlet, and

said air outlet being between said whistle wall and References Cited UNITED STATES PATENTS 6/1957 Vonnegut 73-194(vib) 11/1958 Entwistle 73-203 JERRY W. MYRACLE, Primary Examiner US. Cl. X.R. 

